Decolorizing titanium tetrachloride



Edge! P. Stamhaugh, Metuchen,

tional Lead Company, of New Jersey N9 Drawing. Application May 27, 1952,

Serial No. 290,317

4 Claims. (Cl. 202-57) N. J., assignor to Na- New York, N. Y., a corporation The present invention relates in general to the preparation of the tetrahalides of metals of the fourth group of elements and more especially to the purification of titanium tetrachloride and similar stable normally liquid distillable tetrahalides.

in general the tetrahalides of metals of the fourth group of elements are prepared by chlorinating a metal bearing material, and recovering the metal tetrachloride vapor in the form of a relatively impure liquid condensate. By way of example, liquid titanium tetrachloride is commonly prepared by treating a titaniferous material such as titaniferous iron ore, or ilmenite with chlorine gas, in static bed or fluosolids operation, to form titanium tetrachloride vapor which is subsequently condensed to form a crude titanium tetrachloride condensate. Since there are a number of elements in the raw material, in addition to titanium, which react with chlorine to form volatile chlorides and which carry over with the titanium tetrachloride vapors, the titanium tetrachloride condensate, sometimes hereinafter referred to as crude titanium tetrachloride, is invariably impure. Moreover, it been found that these volatile chlorides are not readily eliminated by distillation since the respective chlorides such as, for example, the chlorides of silicon, aluminum, niobium, tungsten and vanadium tend to distill over with the titanium tetrachloride values and to be found in the condensate. One such impurity which, because of the proximity of its boiling point to that of titanium tetrachioride, cannot be separated therefrom by fractional distiliatic-n is vanadium chloride. Vanadium chloride is present in substantially all crude titanium tetrachloride condensate and comprises a major portion of the impurities in the condensate and hence is chiefly responsible for the yellowish color of crude titanium tetrachloride. By way of example, a typical crude titanium tetrachloride may comprise from 0.25 to 0.35% vanadium based on the weight of the titanium tetrachloride the other impurities being present in relatively small amounts such as, for example, from 0.04 to 0.2% silica, from 0.02 to 0.025% alumina, from 0.01 to 0.02% niobium and from 0.05 to 0.09% tungsten.

While it has been proposed heretofore to purify crude titanium tetrachloride and other similar tetrahalides by treatment with such materials as hydrogen sulphide, silica gel, carbon, salts of the heavy metals, soya bean oil, art

gum, etc. such methods have been characterized by polymerization and the formation of insoluble residues or residues which have been removable from the still bottoms only with the greatest difliculty. As a consequence the adaptation to commercial production of prior methods for purifying crude titanium tetrachloride have been attended by much difficulty and high cost.

An object of the present invention is, -therefore, to provide a superior method for producing substantially pure liquid tetrahalides of the fourth group of elements.

A further object of the invention is to provide a superior method for purifying crude titanium tetrachloride which nited States Patent is convenient, economical and adaptable to commercial production.

A still further object of the invention is to provide a superior method for removing a major portion of the impurities from crude titanium tetrachloride in a manner such that no polymerization occurs and the residue ormed may be readily removed from the still.

These and other objects will become more apparent from the following more complete description of the instant invention.

In its broadest aspects the present invention relates to a process for producing substantially pure liquid titanium tetrachloride by adding small amounts of an alkali metal hydroxide admixed with certain metals, to crude titanium tetrachloride and refluxing the admixture to form a substantially water-white titanium tetrachloride condensate.

The treatment of crude titanium tetrachloride, by which is meant a liquid titanium tetrachloride containing such impurities as vanadium, silica, alumina, niobium, tungsten and the like with an admixture of alkali metal hydroxide and metal, sometimes hereinafter referred to as the purifying composition may be carried out, according to the present invention, in any convenient manner which will insure the required intimacy of contact between the crude titanium tetrachloride and the purifying composition. Preferably the purification treatment is carried out in a purification unit, comprising, for example, a still having a fractionating column, a reflux return and a condenser, by heating an admhtture of the crude titanium tetrachloride, alkali metal hydroxide and metal in the still to a temperature and for a period of time such that substantially all of the titanium tetrachloride and the purifying composition are circulated as vapor through the fractionating column and reflux return; and thereafter allowing the vapor to pass to the condenser in which the titanium tetrachloride will be condensed and collected as a water-white liquid. The heating of the constituents in the still and the recirculation of the vapors is sometimes hereinafter referred to as refluxing and may be facilitated by employing mechanical agitation or bubbling dry inert gases through the constituents.

It will be appreciated that the efliciency and eflicacy of the refluxing operation hereinabove described may be enhanced by first eliminating any suspended colloidal matter and dissolved gases which may be in the crude titanium tetrachloride and which are susceptible to removal by fractional distillation.

The residue which forms in the bottom of the still comprises vanadium and small amounts of silica, alumina, tungsten, niobium and other impurities, the vanadium being in the form of VCls and/or VOC1 which may be recovered from the residue by water leaching. It has been observed that the vanadium content of crude liquid titanium tetrachloride may be reduced by the process of this invention from about 0.35% by Weight of titanium tetrachloride as found in crude titanium tetrachloride to about 0.000l% the purified liquid titanium tetrachloride being water-White. a

The term water-white is used herein to denote a substantially pure titanium tetrachloride condensate. In particular, a titanium tetrachloride condensate purified by the process of this invention and defined as water-White is one having a major portion of its impurities removed, that is to say the maximum vanadium content is in the range from about 0.0001% to 0.0003% by weight of the titanium tetrachloride the remaining impurities in the titanium tetrachloride condensate being present in such small quantities as to be innocuous.

The time and temperature of the treatment is dependent to some extent upon the amount of impurities in the crude titanium tetrachloride and the amount of alkali metal hydroxide and metal used to remove the impurities from the titanium tetrachloride. Moreover, the amount of alkali metal hydroxide and metal used is, in turn, dependent upon the amount of impurities and in particular the amount of vanadium present. in the crude titanium By the process of this invention crude titanium tetrachloride containing impurities the major portion of which is vanadium may be purified by refluxing the titanium tetrachloride in the presence of a relatively small quantity,

tetrachloride. The length of time necessary for efiective based on the amount of titanium tetrachloride, of an adtreatment of the crude liquid titanium tetrachloride varies mixture of an alkali metal hydroxide and a metal, such inversely with the amount of alkali metal hydroxide and as powdered magnesium, aluminum, titanium and sodium. metal added to the crude titanium tetrachloride. For eco- The condensed vapors form a substantially pure waternomical reasons a minimum amount of the purifying comwhite titanium tetrachloride condensate. The process is position is preferred for eiiecting substantially complete 10 carried out in an economical and commercially practical purification of the crude titanium tetrachloride and where manner and while it has been described with particular the amount of the purifying composition added reference to the treatment of titanium tetrachlorid'e'it is is, for example, substantially 0.15 to 0.2% based on the not to be so limited since other tetrahalides of'the metals weight of the crude titanium tetrachloride the time re- 0f the fourth group of element maybe purified in a similar quiredfor refluxing a mixture of crude titanium tetramann rchloride and the purifying composition is about 2 hours. While this invention has been described and illustrated However, it has been observed that when the amount of by the example shown it is not intended that it be limited purifying composition is substantially 0.25 to 0.3% h thereto and other modifications and variations may be the reflux time is about 1 hour. In short, as the amount of p y Within the Scope of the following spuri'fying composition added to the crude titanium tetra- 29 I la chloride is increased the time required for refluxing the A Process treating el'ude titanium tetrachloride mixture of crude titanium tetrachloride and the purifying t0 remove a major Portion of the i p ri e t er from composition i d d, which comprises admixing the crude titanium tetrachlo- I a i t h treatment f h ud i i ride with a solid alkali metal hydroxide selected from tetrachloride with an alkali metal hydroxide and metal the the 8 P n i ing of d um hydroxide and potassium alkali metal hydroxide and metal are preferably used in hydroxide, and metal selee'lel1 from the group Consistpowdered or granular form, sometimes hereinafter reof Sodium, magnesium, titanium and aluminum; and ferred to as comminuted, and are added to crude titanium refluxing Said admiXtllle in the a sence of Water at a tetrachloride at substantially room temperature whereupon telhllelhml'e and for 3 Period of time Suflieient to Produce the constituents are heated to a temperature of from about 30 a Water-White titanium t tra hl ride condensate. 134 C. to 138 C., and agitated, if necessary, fo a 2. Aprocess for purifying crude titanium tetrachloride period of time generally in the neighborhood of about 2 y removing a major Portion of the Vanadium therefrom hours after which the titanium tetrachloride vapors are which comprises admixing the crude titanium tetrachlocond'ensed to produce a substantially water-White conden- With Small amounts f a mmin lt d alkali metal sate. A treatment time of about 2 hours is usually sufiihydroxide Selected from the group consisting of Sodium cient with the amount of purifying constituents equal to hydroxide and Potassium hydroxide, and a finely divided about 10 to about 30 parts of alkali metal hydroxide, about metal Selected from the group consisting of sodium, 15 to about 20 parts of powdered metal per 1000 parts heshlm, titanium and aluminum, and each 1000 Parts of titanium tetrachloride by weight. of titanium tetrachloride to be treated the alkali metal The following example is illustrative: 40 hydroxide being present in amount from about 10 parts to Examp 18 about 30 parts by weight and the finely divided metal being present in amount from about 1.5 parts to 20 parts by To 3520 parts of crude titanium tetrachloride at subweight; refluxing the admixture in the absence of water at stantially room temperature were added a powdered alkali a temperature and for a period of time suflicient to separate metal hydroxide and a powdered metal, the amounts of a major portion of the vanadium from the titanium tetraalkali metal hydroxide and powdered metal used being chloride; and distilling the refluxed titanium tetrachloride. shown in the table. The constituents were refluxed at a 3. A process for purifying crude titanium tetrachloride temperature of from about 134-138 C, for a period of by removing a major portion of the vanadium therefrom from one to two hours and then distilled at normal preswhich comprises admixing the crude titanium tetrachlosure out of contact with the outside atmosphere, The 9 ride with small amounts of a finely divided alkali metal distillate was a substantially water-white titanium tetrahydroxide selected from the group consisting of sodium chloride and the residue formed in the bottom of the still hy roxi e and pot ssium hy roxide and a finely divided comprised water soluble vanadium compounds, rutile, metal Selected from the group consisting of Sodium, ganatase, and minute quantities of other impurities such nesium, titanium and aluminum, and f h 1000 Part as thosed named above. of titanium tetrachloride to be treated the finely divided The following table contains the results f experiments alkali metal hydroxide being present in amount from about run using NaOH and KOH as the alkali metal hydroxide 10 parts to about 30 parts by Weight and the finely divided admixed with powdered metals such as, for example, Na, metal being present in amount from about 1.5 parts to 20 Mg, T1 and Al. parts by weight; refluxing the admixture in the absence of Table Exp. Alkali Metal Hydroxide Metal Parts il fg i e Color of Dlsi ii fi No. Parts at 136 tlllate Distillate,

0., Hours percent ifixhihiifiiiiiit: 3:353 ii glmdiiii 213 31% 2.5% NaOH (powdered)--- 2.0% Ti (granular) 3. 0 0. 0002 3.0% Na0H(powdered) 2.0%A1 (powdered) 2.0 0.0003 1.0% KOH 0.2% Na (wire) 2.0 0. 0003 I 2.0% KOH 2.0% Mg (powdered).- 2.0 0.0003

I Exprssed in percentage based on weight at crude T1014.

water at a temperature of from about 134 C. to about 138 C. and for a period of time from about 1 to about 3 hours to separate a major portion of the vanadium from the titanium tetrachloride; and distilling the refluxed titanium tetrachloride.

4. A process according to claim 2 in which the alkali metal hydroxide is powdered sodium hydroxide and in which the finely divided metal is titanium.

2,178,685 Gage Nov. 7, 1939 6 Jenness et a1. Feb. 4, 1941 Meister Mar. 14, 1944 Cole et al. Mar. 12, 1946 Mei'ster Feb. 18, 1947 Nicholson Ian. 4, 1949 Espenschied July 10, 1951 Espenschied July 10, 1951 Espenschied June 3, 1952 OTHER REFERENCES Chemical Abstracts, volume 16, 1922. Stoddard et a1.: Abstract of application, Serial No. 706,498, published February 21, 1950. 631 O. G. 883. 

1. A PROCESS FOR TREATING CRUDE TITANIUM TETRACHLORIDE TO REMOVE A MAJOR PORTION OF THE IMPURITIES THEREFROM WHICH COMPRISES ADMIXING THE CRUDE TITANIUM TETRACHLORIDE WITH A SOLID ALKALI METAL HYDROXIDE SELECTED FROM THE GROUP CONSISTING OF SODIUM HYDROXIDE AND PATASSIUM HYDROXIDE, AND A METAL SELECTED FROM THE GROUP CONSISTING OF SODIUM, MAGNESIUM, TITANIUM AND ALUMINUM; AND REFLUXING SAID ADMIXTURE IN THE ADSENCE OF WATER AT A TEMPERATURE AND FOR A PERIOD OF TIME SUFFICIENT TO PRODUCE A WATER-WHITE TITANIUM TETRACHLORIDE CONDENSATE. 